GB191309261A - Improvements in or relating to Alternating Current Dynamo-electric Machines adapted for Synchronous Working. - Google Patents

Abstract

9261. Hunt, L. J., and Sandycroft, Ltd. April 19. Alternating - current induction m a c h i n e s ; motors, controlling; exciting; windings. - An alternating-current synchronous machine is started as an induction motor by means of the arrangements shown in Specification 16,170/09 by running up to synchronism with the windings connected so as to give one of the basal pole numbers, and then altering the connexions so that the machine runs in cascade, which corresponds to synchronous speed, direct current being at the same time supplied to the stator. Fig. 1 is a diagram of the stator windings comprising a three-phase winding supplied through terminals 5, 6, 7, and star-connected at 8, and a direct-current winding having terminals 9, 10. The rotor connexions, Fig. 2, are similar to those in Fig. 14 of Specification 16,170/09, the slip-rings 16 being connected to a regulator 14, and the star connexions being brought out by slip-rings 11 to a starting-switch 13. At starting, the slip-rings 16 are connected by the regulator 14, thus giving a basal pole number, for example four, on the rotor which is by this means run up to synchronous speed. The regulator 14 is then opened, thus changing the rotor connexions to cascade working, for example six pole, and direct current is supplied to the terminals 9, 10. The alternating and direct current windings may be combined by taking tappings 21, 22, 23, Fig. 3, from the star winding, and supplying any or all, for example 21, 22, from separate commutators 27, 28 through regulators 29, 30, the remaining point or points, such as 23, being short-circuited by a switch 24. The commutators 27, 28 may be those of separate generators, or may be common to a single generator 26 having two wave windings arranged in the same slots of an ordinary armature, two of the coils being left dead if the number of slots be even. The invention is also applicable to the case of two machines connected in cascade, and, according to the Provisional Specification, to synchronous generators.